This is a combination of prior application Ser. No. 832,735 filed Feb. 25, 1988 by Giuseppe Marchionni and Gian Tommaso Viola and application Ser. No. 917,550 filed Oct. 10, 1986 by Giulio Tommasi, Raffaele Ferro and Gianna Cirillo.
This invention relates to new perfluoropolyethers having a Br atom bound to one or both the end groups of the chain.
More in particular this invention relates to new mono- or bifunctional perfluoropolyethers having a controlled molecular weight and consisting of units chosen from amongst ##STR2## statistically distributed along the perfluoropolyether chain.
A further object of the present invention is that of providing a process for preparing the abovesaid perfluoropolyethers with brominated end groups and having a controlled molecular weight by a method which is easily practicable on a commercial scale and is capable of providing high yields of brominated product.
It is known that the reaction of oxygen with tetrafluoroethylene and/or perfluoropropene, carried out at a low temperature in the presence of UV radiations and in an inert solution, generally a fully fluorinated compound or a chlorofluorinated compound, leads to a perfluoroether product having a peroxide oxygen content which varies as a function of the operative conditions under which the photooxidation has been effected.
The process and the peroxidic products are disclosed for example in British Patent Nos. 1,226,566 and 1,104,482.
The thermal decomposition of the peroxide, which is carried out to remote peroxide bridges containing neutral end groups of the type --CF.sub.3, CF.sub.2 CF.sub.3 and acylic end groups of the type --OCF.sub.2 COF.
Actually, the thermal decomposition reaction of the peroxide product for providing the neutral perfluoropolyether gives rise to radicals of the type R.sub.f O--CF.sub.2 (RF being a perfluoroether chain), which react with one another, thus leading always to perfluoropolyethers having a high and non-controlled molecular weight.
The decomposition of the peroxidized precursors is usually carried out by a heat treatment carried out in a wide temperature range, generally from about 100.degree. C. up to high temperatures, preferably from 180.degree. to 250.degree. C.